1. Field of the Invention
The present invention generally relates to flash memory apparatus, in particular, to a data erasing method for the flash memory apparatus.
2. Description of Related Art
As continuously developing in electronic technology, the electronic products have been the tools without missing in daily life. In order to provide sufficient information, the electronic product usually needs to implement with the storage medium, which is in higher speed and bigger storage capacity to store data. So, the non-volatile flash memory for accessing data has played an essential role.
In the conventional technology, when a data erasing operation is intended to erase data of the memory cells of the flash memory, it needs to erase all data of the memory cells in the whole block. FIG. 1 is a drawing, schematically illustrating the threshold voltage distribution of the memory cells in the flash memory. As referring to FIG. 1, it includes the memory cells at the erased state ERS and the memory cells at the programmed state PGS. The data erasing operation by incremental stepping pulse erase (ISPE) is usually used in the conventional technology to erase memory cells. Further, this conventional data erasing operation uses voltage pulses with incremental voltages to perform multiple data erasing operations on the memory cells. However, the voltage pulses with large voltage level would cause the drift speed of the threshold voltage for a portion of memory cells to be too fast, resulting in out of control due to over-large range of the threshold voltage distribution of the erased memory cells.